Electrical Characteristics of Time-Dependent Flexible Organic Ferroelectric Field-Effect Transistors

Organic ferroelectric field-effect transistors (Fe-FETs) are highly attractive for memory device applications because of their ability to read data without causing damage (nondestructive readout) and their excellent retention capabilities. These attributes make organic Fe-FETs an appealing alternative to their inorganic counterparts, which, while demonstrating superior memory performance for practical applications, still have significant challenges. This study investigates the impact of solvent selection and dielectric properties on the electrical characteristics, memory window, and long-term stability of flexible organic Fe-FETs. To this end, the electrical characteristics of devices fabricated using various organic solvents (dimethylformamide (DMF) and 2-butanone/ethyl methyl ketone (MEK)) were compared, and the results revealed that devices using polyvinylidene fluoride trifluoro ethylene (P(VDF-TrFE)) and Polyvinylidene fluoride hexafluoro-propylene (P(VDF-HFP)) in DMF exhibited higher drain currents with a larger memory window. This can be attributed to the relatively smoother surface morphology of ferroelectric films prepared with DMF. The time-dependent electrical properties of various flexible organic devices were investigated and the memory window of flexible Fe-FETs with a P(VDF-TrFE) dielectric layer exhibited excellent electrical stability. For the device with the P(VDF-HFP) dielectric, extracted memory windows (ΔVth) decreased from 25.1 to 19.0 V after two weeks. The electrical properties of P(VDF-TrFE) and P(VDF-HFP) dielectric layers exhibited entirely different tendencies depending on the solvent polarity, with the relatively simple molecular structure of the P(VDF-TrFE) film demonstrating higher electrical reliability. These results underscore the significant impact of solvent selection and the properties of the dielectric–semiconductor interface on the long-term reliability and operational efficiency of flexible Fe-FET devices.